1. Field of the Invention
The present invention relates to a light source apparatus and a method of controlling the same.
2. Description of the Related Art
A color image display apparatus is available that includes a color liquid crystal panel having a color filter and a light source apparatus (backlight apparatus) that emits white light to aback surface of the color liquid crystal panel is known.
Conventionally, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) is mainly used as a light-emitting element of the light source apparatus. However, in recent years, a light emitting diode (LED), which is excellent in power consumption reduction, service life, color reproducibility, and environmental load reduction, is used as the light-emitting element of the light source apparatus.
A light source apparatus (LED backlight apparatus) which uses LEDs as the light-emitting element includes a number of LEDs. Japanese Patent Application Publication No. 2001-142409 discloses a LED backlight apparatus which has a plurality of light sources each including at least one LED. Moreover, Japanese Patent Application Publication No. 2001-142409 discloses that emission brightness of a light source is controlled in respective light sources. The emission brightness of a light source that emits light to a region of the screen of a color image display apparatus in which a dark image is displayed is decreased, whereby the power consumption decreases and the contrast of the image is improved. Such brightness control in respective light sources according to image characteristics is referred to as local dimming control.
In a light source apparatus, there is a problem that the emission brightness of a light source changes. The emission brightness changes, for example, due to a change in emission characteristics of a light-emitting element resulting from a change in temperature, aging of the light-emitting element, and the like. In a light-emitting apparatus having a plurality of light sources, as a result of variation in the temperature and the degree of aging among the light sources, the emission brightness of the plurality of light sources are varied (becomes uneven).
As a method of suppressing a change in the emission brightness and a brightness unevenness, a method of adjusting the emission brightness of the light source using an optical sensor is known. Specifically, a method of providing an optical sensor that detects reflection light which has been reflected from an optical sheet (optical member) provided in a light source apparatus among light beams emitted from the light source apparatus and has returned toward the light source and adjusting emission brightness of the light source based on a detection value (optical detection value) of the optical sensor is known. In a light-emitting apparatus having a plurality of light sources, individual light source lighting-control is performed such that a plurality of light sources is sequentially selected and only the selected light source is lit. When each light source is subjected to such individual light source lighting-control, light (specifically, reflection light) from the light source is detected by the optical sensor. After that, the emission brightnesses of respective light sources are adjusted based on the optical detection value of each light source. Such a technique is disclosed in Japanese Patent Application Publication No. 2011-27941.